Citation and License

Arthritis Research & Therapy 2012, 14:R15
doi:10.1186/ar3694

Published: 20 January 2012

Abstract

Introduction

Cartilage oligomeric matrix protein (COMP) is found at elevated concentrations in
sera of patients with joint diseases such as rheumatoid arthritis (RA) and osteoarthritis
(OA). We recently showed that COMP activates complement via the alternative pathway
and that COMP-C3b complexes are present in sera of RA patients, but not in healthy
controls. We now set out to elaborate on the information provided by this marker in
a variety of diseases and larger patient cohorts.

Methods

COMP-C3b levels in sera were measured by using an enzyme-linked immunosorbent assay
(ELISA) capturing COMP and detecting C3b. Serum COMP was measured by using ELISA.

Results

COMP-C3b levels were significantly elevated in patients with RA as well as in systemic
lupus erythematosus (SLE), compared with healthy controls. SLE patients with arthritis
had significantly higher COMP-C3b levels than did those without. COMP-C3b was furthermore
elevated in patients with ankylosing spondylitis (AS), psoriatic arthritis (PsA),
reactive arthritis, systemic sclerosis, and OA. COMP-C3b did not correlate with COMP
in any of the patient groups. COMP-C3b correlated with disease activity in RA, but
not in other diseases. COMP-C3b levels in RA patients decreased on treatment with
tumor necrosis factor (TNF)-α inhibitors, whereas the levels increased in patients
with AS or PsA. The changes of COMP-C3b did not parallel the changes of C-reactive
protein (CRP).

Conclusions

COMP-C3b levels are elevated in several rheumatologic diseases and correlate with
inflammatory measures in RA. COMP-C3b levels in RA decrease during TNF-α inhibition
differently from those of CRP, suggesting that formation of COMP-C3b relates to disease
features not reflected by general inflammation measures.